A SpaceX Falcon 9 rocket lifted off on December 15, 2017, from Cape Canaveral Air Force Station. The rocket carried a SpaceX Dragon laden with 4,800 pounds of research equipment, cargo, and supplies for the International Space Station.

Once TSIS is mounted on the Space Station and begins operating, data from the sensor will be used to extend a space-based record of total solar irradiance dating back to 1978. It will also extend the observational record for solar spectral irradiance (a more specific measurement) that began in 2003 with the launch of the Solar Radiation and Climate Experiment (SORCE) satellite. Having TSIS collect measurements that overlap with those collected by older missions is critical to reducing uncertainties in long-term records of solar change.

“We need to continue to monitor the Sun over long periods, during which the irradiance may change gradually but significantly,” said Peter Pilewskie, TSIS lead mission scientist from the University of Colorado at Boulder. “How the atmosphere responds to subtle changes in the Sun’s output helps us distinguish between natural and human influences on climate.”